The dose when treating tuberculosis is 150 mg/kg/day divided into two to four daily doses; the usual adult dose is therefore approximately 2 to 4 grams four times a day. It is sold in the US as "Paser" by Jacobus Pharmaceutical, which comes in the form of 4 g packets of delayed-release granules. The drug should be taken with acid food or drink (orange, apple or tomato juice).[4] PAS was once available in a combination formula with isoniazid called Pasinah[5] or Pycamisan 33.[6]

The European Medicines Agency (EMA) has recommended granting a marketing authorization for PAS in multidrug-resistant tuberculosis in adults and children when other treatments cannot "be devised for reasons of resistance or tolerability."[7]

PAS was discovered by the Swedish chemist Jörgen Lehmann upon the report that the tuberculosis bacterium avidly metabolized salicylic acid. Lehmann first tried PAS as an oral TB therapy late in 1944. The first patient made a dramatic recovery.[14] The drug proved better than streptomycin, which had nerve toxicity and to which TB could easily develop resistance. In the 1948, researchers at Britain's Medical Research Council demonstrated that combined treatment with streptomycin and PAS was superior to either drug alone.[1]

PAS has been shown to be a pro-drug and it is incorporated into the folate pathway by dihydropteroate synthase (DHPS) and dihydrofolate synthase (DHFS) to generate a hydroxyl dihydrofolate antimetabolite, which in turn inhibits DHFR enzymatic activity.[15]

^ abcFox, W.; Ellard, G. A.; Mitchison, D. A. (1999). "Studies on the treatment of tuberculosis undertaken by the British Medical Research Council tuberculosis units, 1946-1986, with relevant subsequent publications". The international journal of tuberculosis and lung disease : the official journal of the International Union against Tuberculosis and Lung Disease3 (10 Suppl 2): S231–S279. PMID10529902.edit